Several designs are known in the prior art for fluid control valves which have reduced flow resistance. German Patent No. 1,213,187 discloses a valve with a movable internal slide. The slide is connected on one side to a flexible hose. The opposite side of the slide is adjacent outlet ports in the valve body. Fluid passes from the hose through the slide. By shifting the position of the slide, fluid is selectively delivered to the outlet ports. The slide is spring loaded against the outlet ports to avoid fluid loss. A polished metal insert is used to enable movement of the slide across the outlet ports and to avoid excessive wear. A drawback associated with this design is that the slide must be spring loaded which necessitates the use of considerable force to shift the slide. The actuator portion of the valve which moves the slide must therefore be operated at high pressure or must be sufficiently large to produce the required force at low pressures.
German Patent No. 1,288,389 also discloses a valve having an internal slide. The slide is housed within the valve body and is moved between locations inside the valve to direct fluid to selected outlet ports. The slide must be highly polished and in close tolerance with the interior of the valve body to achieve sealing and avoid fluid loss. This valve construction poses significant resistance to flow and would be expensive to produce.
U.S. Pat. No. 4,526,202 discloses a low resistance valve which includes an internal sliding member. The member is connected to a flexible hose inside the valve body. Fluid enters the valve and is directed through the flexible hose and slide portions to an outlet port. An alternative form of the valve employs a seal between the sliding member and the outlet port to minimize fluid loss. It is expected that a valve made in accordance with this design would pose reliability problems due to the use of an internal flexible hose member.
Two designs for low restriction fluid control valves are disclosed in U.S. Pat. No. 4,458,238. One such design uses a rotatable rocker member to direct fluid from an inlet port to a selected outlet port. Due to the rotatable nature of the rocking member, it would be difficult to avoid fluid loss inside the valve. Another design disclosed in this patent employs a slider member which moves longitudinally to direct fluid to selected outlet ports. The slider member is spring loaded or made in very close tolerance with the cavity in which it is housed to avoid fluid losses. This valve would require high force to shift the sliding member and would be expensive to produce.
Thus, there exists a need for a low restriction directional fluid control valve which can be made inexpensively, which has low internal fluid loss, is reliable and which can be operated at lower pressures than valves known in the prior art.